Neonatal hypothyroidism is decreased thyroid hormone production in a newborn. In very rare cases, no thyroid hormone is produced. The condition is also called congenital hypothyroidism. Congenital means present from birth.
Hypothyroidism in the newborn may be caused by:
A thyroid gland that is not fully developed is the most common defect. Girls are affected twice as often as boys.
Most affected infants have few or no symptoms. This is because their thyroid hormone level is only slightly low. Infants with severe hypothyroidism often have a unique appearance, including:
This appearance often develops as the disease gets worse.
The child may also have:
A physical exam of the infant may show:
Blood tests are done to check thyroid function. Other tests may include:
Early diagnosis is very important. Most of the effects of hypothyroidism are easy to reverse. For this reason, most US states require that all newborns be screened for hypothyroidism.
Thyroxine is usually given to treat hypothyroidism. Once the child starts taking this medicine, blood tests are regularly done to make sure thyroid hormone levels are in a normal range.
Getting diagnosed early usually leads to a good outcome. Newborns diagnosed and treated in the first month or so usually have normal intelligence.
Untreated mild hypothyroidism can lead to severe intellectual disability and growth problems. The nervous system goes through important development during the first few months after birth. Lack of thyroid hormones can cause damage that cannot be reversed.
Call your health care provider if:
If a pregnant woman takes radioactive iodine for thyroid cancer, the thyroid gland may be destroyed in the developing fetus. Infants whose mothers have taken such medicines should be observed carefully after birth for signs of hypothyroidism. Also, pregnant women should not avoid iodine-supplemented salt.
Most states require a routine screening test to check all newborns for hypothyroidism. If your state does not have this requirement, ask your provider if your newborn should be screened.
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.